Electronic equipment such as televisions, telephones, radios, and computers are often constructed using semiconductor components, such as integrated circuits, memory chips, and the like. The semiconductor components are typically constructed from various microelectronic devices fabricated on a semiconductor substrate, such as transistors, capacitors, diodes, resistors, and the like. Each microelectronic device is typically a pattern of conductive, semiconductive, and insulator regions formed on the semiconductor substrate.
The density of the microelectronic devices on the semiconductor substrate may be increased by decreasing the size, or linewidth, of the various semiconductor devices. The decrease in linewidth allows a larger number of such microelectronic devices to be formed on the semiconductor substrate. As a result, the computing power and speed of the semiconductor component may be greatly improved.
In order to decrease the linewidth of the microelectronic device, the size and thickness of the conductor, semiconductor, and insulator regions forming each microelectronic device must be reduced. As the size of the microelectronic device is scaled down to sub-micron sizes, salicidation of the contact surfaces between conductive regions becomes increasingly difficult. Salicidation is the process of forming a self-aligned region comprising a conductive silicide material. This region is useful, for example, in reducing the electrical contact resistance between conductive contacts. One form of salicidation uses titanium silicide. The sheet resistance of titanium silicide increases as the linewidth decreases. Salicidation of a gate of a transistor is an area in which the increased sheet resistance is particularly problematic.
Some methods of salicidation amorphize the outer surface of the layer forming the gate conductor in order to reduce the sheet resistance of the titanium silicide. However, these amorphization methods can damage the source and drain components of the transistor. The damage to the transistor may result in an increase of the series resistance and a decrease of the device drive current, thereby decreasing the performance of the transistor.